"Force field" helps patients with spinal cord injuries regain strength

Whether developed from a traumatic accident or from a disease like spina bifida, spinal cord injuries (SCI) are debilitating and can cause loss of mobility and feeling in patients who suffer from them. As a result, these patients, especially those 65 and older, can struggle to participate in social activities unassisted. But scientists from Columbia Engineering have now designed a new rehabilitation tool that they hope can help patients regain some of their autonomy and mobility.

The new study, published Monday in the journal Spinal Cord Series and Cases looks at how an “assist-as-needed” technology could allow users to gain more strength when sitting. The device, called TruST (Trunk-Support Trainer), is attached to patients near the ribs and is designed to provide support when a patient goes outside their pre-designated area of movement (aka, when they’re about to fall).

Study co-author and professor of mechanical engineering and of rehabilitation and regenerative medicine at Columbia, Sunil Agrawal, said in a statement that TruST can help patients gain mobility as well as prevent them from falling and injuring themselves.

“We designed TruST for people with SCIs who are typically wheelchair users,” said Agrawal. “We found that TruST not only prevents patients from falling, but also maximizes trunk movements beyond patients’ postural control, or balance limits.”

But, in order to help patients push beyond their balance and mobility limits, researchers first had to establish where those limits were. To do this they worked with a sample group of five SCI patients (two male and three female with an average age of 60) and tested their baseline mobility by evaluating how far they could move their torsos (while following a ball with their heads) in a star-like shape without losing their balance. Once those boundaries were established, the team introduced TruST.

When the patients completed the same star-like movement patterns with TruST the researchers found that their mobility increased on average 25 percent (although not equally in all directions.) This can be attributed to the fact that as patients moved closer to and beyond their predefined mobility limits TruST would apply an assistive “force field” pressure of two and then five percent the patient’s body weight. This support allowed the patient to maintain balance beyond their initial range of mobility.

Physical therapist, postdoctoral researcher, and the study’s first author, Victor Santamaria, said in a statement that the successes demonstrated in this study show promise for future rehabilitation plans with TruST down the line.

“The capacity of TruST to deliver continuous force-feedback personalized for the user’s postural limits opens new frontiers to implement motor learning-based paradigms to retrain functional sitting in people with SCI,” said Santamaria. “We think TruST is a very promising SCI rehab tool.”

Part of TruST’s role as a rehab tool that the team is already exploring, said Agrawal, is to create a training paradigm around it for adults and children that will help them improve trunk control.

“The robotic platform will be used to train participants with SCI by challenging them to move their trunk over a larger workspace, with TruST providing assist-as-needed force fields to safely bring the subjects back to their neutral sitting posture,” said Agrawal. “This force field will be adjusted to the needs of the participants over time as they improve their workspace and posture control.”

The authors write in the study that they hope the increased mobility provided by TruST can help these patients more easily participate activities in their everyday lives that bring them happiness.

Read the abstract here:

Objectives:

To measure and expand the sitting workspace of participants with spinal cord injury (SCI) with the Trunk-Support-Trainer (TruST).

Setting:

Columbia University.

Methods:

TruST is a motorized-cable belt placed around the torso. Participants performed maximal trunk excursions along eight directions, radiating in a star-shape, to define their seated postural limits and workspace area (cm2). TruST was configured to apply “assist-as-needed” forces when the trunk moved beyond these postural limits. Kinematics were collected to examine trunk control. The clinical features of the sample (n = 5) were documented by neurological injury, dynamometry, the American Spinal Injury Association Impairment Scale, and Spinal Cord Independence Measure-III.

Results:

Statistical significance was examined with paired t-tests. TruST successfully recreated the postural limits of participants and expanded their active sitting workspace (Mean: 123.3 ± SE: 42.8 cm2, p < 0.05). Furthermore, participants improved their trunk excursions to posterior (Mean: 5.1 ± SE: 0.8 cm, p < 0.01), right (Mean: 3.1 ± SE: 1.1 cm, p < 0.05), and left (Mean: 5.0 ± SE: 1.7 cm, p = 0.05) directions with TruST-force field.

Conclusions:

TruST can accurately define and expand the active seated workspace of people with SCI during volitional trunk movements. The capacity of TruST to deliver continuous force-feedback at the user’s postural limits opens new frontiers to implement motor learning-based paradigms to retrain functional sitting in people with SCI.